docs: brain-ratified D8 (per-request LoRA) + final DESIGN/PLAN/README deltas

docs: add studio screenshot to README

Shorten Space short_description to <=60 chars

ZeroGPU readiness: module-level cuda preload + all-resident on 48GB card + Space metadata

Scaffold qwen-voice-studio: Qwen3-TTS core, Gradio studio app, design docs